net: add debug check in skb_reset_mac_header()

dcaratti · dcaratti · commit e0052b8b09d2 · 2025-07-18T11:27:51.000+02:00
JIRA: https://issues.redhat.com/browse/RHEL-96625 Upstream Status: net-next.git commit 3b6167e commit 3b6167e Author: Eric Dumazet <edumazet@google.com> Date: Tue Nov 5 17:44:03 2024 +0000 net: add debug check in skb_reset_mac_header() Make sure (skb->data - skb->head) can fit in skb->mac_header This needs CONFIG_DEBUG_NET=y. Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Joe Damato <jdamato@fastly.com> Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Link: https://patch.msgid.link/20241105174403.850330-8-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Davide Caratti <dcaratti@redhat.com>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
@@ -3055,7 +3055,10 @@ static inline void skb_unset_mac_header(struct sk_buff *skb)
 
 static inline void skb_reset_mac_header(struct sk_buff *skb)
 {
-	skb->mac_header = skb->data - skb->head;
+	long offset = skb->data - skb->head;
+
+	DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->mac_header))offset);
+	skb->mac_header = offset;
 }
 
 static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)

Original file line number	Diff line number	Diff line change
`@@ -3055,7 +3055,10 @@ static inline void skb_unset_mac_header(struct sk_buff *skb)`
`3055`	`3055`
`3056`	`3056`	`static inline void skb_reset_mac_header(struct sk_buff *skb)`
`3057`	`3057`	`{`
`3058`		`- skb->mac_header = skb->data - skb->head;`
	`3058`	`+ long offset = skb->data - skb->head;`
	`3059`	`+`
	`3060`	`+ DEBUG_NET_WARN_ON_ONCE(offset != (typeof(skb->mac_header))offset);`
	`3061`	`+ skb->mac_header = offset;`
`3059`	`3062`	`}`
`3060`	`3063`
`3061`	`3064`	`static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)`